erratic idle and a slight knocky sound !

[mad marc]

hi guys , just to let you know what i found when i removed the rocker cover to replace the head gasket on my gs500 k2,
i had just removed the rocker cover and was removing the cams, when i noticed that  the journal cap ( B )  had a hair line fracture in it,  were up on removing  it,  it fell apart it two halfs,   bloody hell that was lucky  it didnt fall in to the crank or  even worse it didnt break off in the crank  when i was at spped.

i have  had a good look at the other three journal caps and they seem ok,  but i may replace all of them  just in case ,  has any one else  known of these to break, there  seems to be  NO  pitting, gouges, chips or dents  or any other problems with the broken journal   clamp, apart from it is in two halfs, i have  looked at the journal cap  under a microscope and it seems very  pourous, and  with very small holes  concentrated at the centre  of  the journal clamp, i  guess  it was a bad  casting ?       any thoughts.

could this be the root of my problems, the knocky sound at idle that goes at revs, the slight drop in revs now  and then,  and the slight backfire  now and then,  the  very  slight  leak  in the  head gasket  was on the same side as the broken journal clamp.

any thougths   on this is much    appreciated,  and has any one else  ever had one of these go for no apparent reason ?